1. Field of the Invention
The present invention relates to an ink tank and an ink jet printer. More particularly, the invention relates to an ink jet printer capable of detecting the presence and absence of the ink tank to be installed stationarily in a printer, and the presence and absence of liquid as well. The invention also relates to an ink tank to be used for such printer.
2. Related Background Art
Conventionally, as the ink-availability detection mechanism for an ink tank that contains ink, there has been known the one that measures the electric conductivity between electrodes with the provision of electrodes in an ink tank as disclosed in the specification of Japanese Patent Application Laid-Open No. 06-286160, for example or means for detecting the presence and absence of ink optically.
However, the unavailability of ink is detected, and when the user replaces ink tanks, the ink tank is removed from the printer for a long time so as to cause the ink lead-out port of the printer to be released to the air outside. Then, there occurs a fear that ink component is solidified in the ink lead-out port, and the communication of ink is impeded when connecting an ink tank again. Also, the quality of ink in the lead-out port and in the ink supply path is caused to change, and there is a fear that when an ink tank is connected again, such ink flows into the head so as to destroy the head eventually. To prevent such event, it is arranged for the printer to detect the presence and absence of ink tank, and a system is provided for the printer to give warning to the user, if the status where the ink tank has been removed should continue for a long time.
Means for detecting the presence and absence of ink tank have been proposed conventionally in some forms. For example, as disclosed in the specification of Japanese Patent Application Laid-Open No. 09-174877, it is possible to detect the presence and absence of ink, and the presence and absence of ink tank as well by use of one optical sensor provided for a printer where the ink tank is arranged on a carriage and the ink tank moves along the movement of the carriage. Also, in this case, it is possible to detect the presence and absence of ink and those of ink tank even if the arrangement is made so that ink tanks are individually provided to deal with plural colors.
However, ink tank is stationarily installed in a printer, it is required to arrange optical sensors in a number of two times the numbers of ink tanks or to make the sensor movable if it is intended to detect the presence and absence of ink in the ink tank, and also, to detect the presence and absence of the ink tank. This inevitably leads to the problem that such system is extremely expensive.